The invention relates to a method for calibrating a multiphase, in particular three-phase inverter, in particular a pulse-controlled inverter, which has, for each of its phases, in each case one switching element on the high-voltage side and in each case one switching element on the low-voltage side and, for at least two of the phases, in each case one current sensor.
In addition, the invention relates to an apparatus for operating such an inverter, and to a computer program and to a computer program product.
For actuating electric machines, in particular for actuating polyphase machines, inverters are provided which supply current to three in particular star-connected or delta-connected phases of the electric machine. Generally, such inverters have, for each of the phases, a switching element on the high-voltage side and a switching element on the low-voltage side, which switching elements are switchable independently of one another and form a bridge circuit for actuating the electric machine. Typically, a current sensor is assigned to at least two of the phases and is connected downstream of the inverter in order to detect the current provided by the inverter. Errors in the measured currents result firstly in errors in the calculated torques of the electric machine and secondly also in torque oscillations which have a negative effect on a drive response of the electric machine. In order to improve the accuracy of the current detection, often calibration of the inverter or of the current sensor system thereof is implemented, wherein offset errors of the current sensor system are generally detected in the deenergized state, i.e. when all of the switching elements of the inverter are open and the electric machine is not rotating. In this case, the current is measured and then the measured value is used to compensate for an offset of the current sensor system.